public void CanSetMultipleFormulas()
        {
            var            mapping = new HbmElement();
            IElementMapper mapper  = new ElementMapper(typeof(Element), mapping);

            mapper.Formulas("formula1", "formula2", "formula3");

            Assert.That(mapping.formula, Is.Null);
            Assert.That(mapping.Items, Has.Length.EqualTo(3));
            Assert.That(
                mapping.Items.Cast <HbmFormula>().Select(f => f.Text.Single()),
                Is.EquivalentTo(new[] { "formula1", "formula2", "formula3" }));
        }